Re: Spectrophotometer measurements
Re: Spectrophotometer measurements
- Subject: Re: Spectrophotometer measurements
- From: bruce fraser <email@hidden>
- Date: Fri, 5 Jul 2002 10:48:52 -0700
At 1:28 PM -0400 7/5/02, email@hidden wrote:
How critical is it to place a piece of blank media underneath the chart
when taking measurements on, say a Gretag MacBeth SpectroScan? For remote
profiling purposes this would require you have on hand every kind of paper,
unless your client is nice enough to include an extra sheet.
Is this necessary? How would it affect the accuracy of the measurements?
It depends very much on the paper stock in question. With a realy
opaque paper, it shouldn't be necessary. With more translucent
papers, it ranges from desirable to essential. In the most extreme
case I've encountered so far, the difference amounted to 9 units in
L* between measuring on the black table of the Spectroscan and
measuring on a stack of paper white. (Measuring over an opaque white
paper overestimated the L* of white by 2 units, so it's probably a
slightly better fallback position than measuring over black.
A reasonably good rule of thumb is that if you can see the white
registration marks on the spectroscan table through the paper, you
need to measure over a stack of paper, and if you can't, you don't.
With some papers, one extra sheet isn't enough -- it will help, but
more would be better.
Your mileage may vary...
Bruce
--
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